CVE-2026-54576: midnightbsd mport Link Following

Vulnerability summary

CVE-2026-54576 is a medium (CVSS 5.8) Link Following vulnerability in midnightbsd mport. EPSS estimates a 0.10% chance of exploitation in the next 30 days, higher than 0.9% of scored vulnerabilities.

Timeline

1. 17-09-2026
   PublishedVulnerability first disclosed.
2. 18-09-2026
   Last modifiedVulnerability information updated.

Description

mport is the MidnightBSD Package Manager. Prior to 2.7.8, do_actual_install() in libmport/bundle_read_install_pkg.c used path-based lstat(), chown(), stat(), and chmod() operations while installing package files. A local attacker with write access to a target directory could replace a checked file with a symlink before privileged ownership or mode changes were applied, redirecting those changes to an attacker-selected path and compromising filesystem integrity or permissions. This issue is fixed in version 2.7.8.

• CWE-59Improper Link Resolution Before File Access ('Link Following')The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.
• CWE-367Time-of-check Time-of-use (TOCTOU) Race ConditionThe product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.